1. Field of the Invention
The present invention relates to a recording tape cartridge which accommodates, in a case, a single reel onto which recording tape such as a magnetic tape or the like is wound, principally for use as a recording/replaying medium for computers and the like.
2. Description of the Related Art
A recording tape cartridge at which a magnetic tape or the like, which is used as a data recording/replaying medium for computers or the like, is wound onto a single reel and this reel is rotatably accommodated in a case made of synthetic resin has been well known hitherto. At a time of use of such a recording tape cartridge (when the cartridge is loaded in a drive device), the reel is rotatable in the case, and at a time of non-use (when the cartridge is not loaded in a drive device), the reel is locked so as to be non-rotatable in the case.
Specifically, such a recording tape cartridge is equipped with a brake mechanism such that the reel does not rotate in the case at times of non-use. Structures in which, for example, a brake member which is non-rotatable with respect to a case is engaged with a reel and suchlike have been considered.
For example, as shown in FIG. 21, a brake member 130 is formed in a circular plate form which is accommodated in a reel hub 112 of a reel 110. The reel hub 112 has the form of a circular tube with a base. The brake member 130 can move up and down in the reel hub 112. A pair of engaging protrusions 134, which are formed substantially in ‘U’ shapes in plan view, are provided standing from an upper face of the brake member 130. A pair of rotation-limiting ribs 126, which protrude down from an inner face of an upper case 122, are inserted into the engaging protrusions 134 and render the brake member 130 non-rotatable with respect to a case 120.
This brake member 130 is continuously urged toward a base wall 114 of the reel hub 112 by an urging member, such as a compression coil spring 116 or the like. Thus, an annular braking gear 132, which is formed at a lower face of the brake member 130, meshes with an annular engaging gear 118, which is formed at an upper face of the base wall 114 of the reel hub 112. As a result, undesired rotation of the reel 110 is prevented.
Further, a circular column-form operation protrusion 136 is provided protruding from a central portion of a lower face of this brake member 130. The operation protrusion 136 is inserted into a through-hole 114A, which is formed through a central portion of the base wall 114 of the reel hub 112, and opposes a gear aperture 128, which is formed at a substantially central portion of a lower case 124. Accordingly, when the reel 110 is to be rendered rotatable, the operation protrusion 136 (and thus the brake member 130) is pushed upward and the meshing of the braking gear 132 with the engaging gear 118 is released (see, for example, the specification of U.S. Pat. No. 6,452,747).
However, with this kind of structure, at times of non-use of the recording tape cartridge, it is possible for the reel 110 to be lifted in opposition to the urging force of the urging member such as the compression coil spring 116 or the like (i.e., the reel 110 is movable in an axial direction thereof). In consequence, if the base wall 114 of the reel hub 112 is moved upward due to impact being applied to the recording tape cartridge due to falling or the like, the brake member 130 may get caught up on a peripheral edge portion of the through-hole 114A (i.e., be tipped up) in an inclined state, as shown in FIG. 21.
If the recording tape cartridge is loaded into a drive device in such a state, there is a problem in that, as well as recording and replaying not being possible, damage to the recording tape cartridge and/or malfunctioning of the drive device may result. Furthermore, because the reel is rotatable at times of non-use, there is a problem in that adverse effects such as the recording tape becoming creased or broken may occur. Further yet, a gap between an upper flange and a lower flange of the reel is set to be substantially equal to the width of the recording tape. Therefore, there is a problem in that if the reel is shaken in the case by falling (dropping) or the like, outer peripheral edges of the upper flange and/or the lower flange may come into contact with inner faces of the case and be deformed, and adverse effects such as twisting or the like of the recording tape will result.
Accordingly, provision, at an inner face of a ceiling plate of a case, of a locking mechanism which prevents lifting of a reel such that the reel cannot be lifted (i.e., is not movable in the axial direction) at times of non-use of a recording tape cartridge has been considered. However, in many such locking mechanisms, an urging member such as a spring or the like is provided, and urging force from this urging member may, via a braking member, cause adverse effects to a rotation shaft of a drive device.
Specifically, because the brake member is continuously urged downward by urging force of the compression coil spring, the urging member of the locking mechanism generates a force component in the downward direction, and urging force on the brake member may be increased. Accordingly, when the urging force on the brake member is increased, because the rotation shaft of the drive device lifts the brake member against this urging force and causes the reel to rotate, an excess load corresponding to this increase is applied to the rotating shaft. Thus, there has been a problem in that it has been difficult to stably rotate the reel.